* The basics on branch-office reliability features
Lately, we’ve pointed out the balancing act required to provide branch-office users with reliable access to centralized IT resources while toeing the line on capital and monthly recurring service charges.
We’ve talked to several of the players in the highly competitive branch-office router market to find out what options they offer for backing up lower-end WAN access routers and last-mile circuits. Most make provisions for dial/ISDN backup, full or partial WAN circuit backup, Internet dual-homing, or some combination of these capabilities in their low-end routers (devices with list prices in the $1,300 to $3,000 price range).
For context, the products referred to here are the Adtran NetVanta 3305, the Alcatel OmniAccess 512, the Cisco 1721, the Enterasys 1805 and 1850, and the Quick Eagle 4240. Some of these vendors, of course, have other products that support more high-availability features, but we’re looking at what you can get in terms of reliability in the most competitively priced products.
Adtran, Alcatel, Cisco, and Enterasys support dial and ISDN back-up capabilities. In most cases, you must purchase the internal or external modem or ISDN network terminal adapter separately.
QuickEagle doesn’t support ISDN or dial backup (“there’s not enough bandwidth,” says Madjid Abdi, senior product manager), but does support the Border Gateway Protocol Version 4 (BGP-4) protocol for dual-homing to separate Internet services. Its 4240 also supports multilink frame relay to bond two links together, enabling one to absorb the load if a single physical link should fail.
Some vendors, such as Alcatel, Cisco, and Enterasys, in addition to dial, partial, or full link protection, also support “virtual router” protocols to protect against a failed WAN access router. Alcatel and Enterasys support the IETF’s Virtual Router Redundancy Protocol, while Cisco supports both VRRP and its own Hot Standby Router Protocol, which preserves state information for processes such as IPSec tunnels and Network Address Translation for greater uptime. We’ll look more closely at how these protocols work in a future newsletter.
And an interesting feature of the Enterasys architecture is external compact-flash and internal flash memory, which avoids router disruptions when downloading new software to the devices. Ben McLeod, director of product marketing at the company, explains that the new software image can be downloaded to the external device and then booted during off-hours for minimum impact. The old rev can be maintained on the internal flash memory, in case something should go awry and you need to switch back.
For backup route processor support (RPs are the router brains that contain routing table information), you’ll need to move into higher-end devices starting at about $10,000, though some of the lower-end devices do support dual power supplies.
